Coverage analysis of ultra-dense heterogeneous cellular networks with interference management

Deploying ultra-dense small base stations (SBSs) in the coverage umbrella of a macro base station (MBS) requires proactive users offloading form MBS to SBSs to achieve maximum performance gain in heterogeneous cellular networks. However, it degrades the signal-to-interference-plus-noise ratio (SINR) of the offloaded users due to strong interference received from MBS. To improve users’ SINR, an efficient interference mitigation scheme is required to be used in conjunction with users offloading. Soft frequency reuse (SFR) is an attractive and spectrally efficient interference mitigation scheme that allocates available bandwidth among all cell users associated with kBS\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$k{\text{BS}}$$\end{document}, where k∈(M,S)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$k\in ({\text{M}},{\text{S}})$$\end{document}. To address the problem of interference, we use the SFR scheme together with power control factor (β)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(\beta )$$\end{document} to transmit at different power levels for interior and edge regions of kBS\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$k{\text{BS}}$$\end{document}, i.e., rkiandrke\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$r^i_{k} \,{\text{and}}\, r^e_{k}$$\end{document}, respectively. We further consider uniform and nonuniform SBS distribution in the premises of MBS and analyse the effect of the SFR scheme on the proposed model with the help of Stochastic geometry. Mathematical expressions for coverage probabilities are derived and validated through simulations. Numerical results show that the proposed model achieves better coverage probability due to reduced interference. Moreover, nonuniform SBS distribution together with the SFR scheme further improves the performance gain of the proposed model.